BANAL is a bookkeeping system that allows you to create and track invoices, clients, projects, timesheets, expenses, suppliers, etc. BANAL is also a client/server application so you can keep one set of books on your system while allowing everyone access.

BDAY is a set of Perl scripts to remind you of
upcoming birthdays. It sets up a small database
with the names and birthdays of the people you
can't forget and sends you an email a certain
number of days before that birthday comes up as
well as on that specific day.

The C++ Money class handles all functions for using decimal number monies. It eliminates problems associated with using C/C++ float or double to handle money (e.g., picking up or dropping odd cents due to rounding).

CALAMAR is an accounting program entirely written in Java. It supports multiple clients, a flexible chart of accounts, multiple currencies and VAT. Calamar has been localized for French, German, Polish, and English.

GnuCash allows you to track bank accounts, stocks, income, and expenses. As quick and intuitive to use as a checkbook register, it is based on professional accounting principles to ensure balanced books and accurate reports. It is backed by an active development community and is blossoming into a full-fledged accounting system.

ISPacct (formerly Brickacct) accounts the logfiles which Bintec routers spew out depending upon configurable rules. Logfile-analyzing mail accounting functionality is also included (in beta stage). It has multiple backends like text, HTML, and MySQL. It was designed and used by a small ISP and is geared towards such uses as monthly accounting per IP or per dial-in use.

QHacc is a personal accounting program based on Qt. It features double- or single-entry bookkeeping and a reconciliation window. It also provides support for memorized and split transactions, graphing, reporting, archiving, and scheduled transactions that can be based on the account balance.

SQL-Ledger is a Web-based, multiuser, double entry
accounting system. Data is stored in an SQL
database server. It is customizable and country
independent, with international language support.
It supports inventory with assemblies, BOMs, and
more.